Do tubeless tires hold air without sealant | should you use sealant anyway

Tubeless tires are known or at least advertised as they would hold air on their own without the need of a tube and most manufacturers would go as far as saying tubeless may not even need a sealant because they are practically very immune to punctures and they will pretty much seal on their own without the need of any sealant but that’s not always the case.

And there are a lot of people that use non-UST tires like tubeless-ready tires and conventional tires as tubeless and they often consider them as going tubeless or having a tubeless tire, but in reality, there are major differences between them.

In this article, I will try to cover everything about this topic and hopefully provide you with a better understanding of the topic, okay so here are the topics.

Do tubeless tires need sealant (UST vs NON-UST)

Best sealants for tubeless (UST) tires

Why sealant is necessary for non-UST tires

Which sealants are best for NON-UST or conventional tires

Do tubeless tires need sealant (UST & NON-UST) :

I will briefly go over the difference between UST and NON-UST tires for the people who don’t know anything about them.

UST term is really old for mountain biking and it was used back in the 19’s to refer to tubeless tires that were specifically made tubeless (not tubeless ready or conventional) and they utilized hooked rims.

But as the years progressed the idea is not considered widely useful anymore because tubeless-ready tires and conventional tires came into play because of the sealants and the term has pretty much vanished now.

Okay so the difference between true tubeless and other tires like TBR and conventional tires is basically tubeless tires can hold air without the sealant and other tires would usually need it to either seat the bead properly or prevent slow air leakage from the bead.

So that brings us back to the question do you really need sealant for tubeless (UST tire)?

and the answer is no and yes, technically you don’t need it but take a recommendation and use it because sealant covers the area inside your tires and seals little holes in it which otherwise can create air pockets inside the tire and that can make the tire practically useless.

Tubeless tires have a harder and more durable casing and they have a synthetic rubber casing on the inside that holds helps the tire hold air, while tubeless tires do have an inner layer of the synthetic layer but the casing is usually thinner and porous.

Usually tubeless tires will not leak sealant even on the first attemp at filling sealants like tubeless ready or conventional tires do but if they are the problem is most likely related to poorly applied rim tape or due to a hole in rim tape

But here’s why I said take a recommendation and use the sealant anyway.

Tubeless tires can do okay with or without a sealant but sometimes the inner layer of the tires can get damaged by you or if the sidewalls get thinner while you are riding and grinding so when that happens the air can actually slip into the inner layer of the tires and it will form bubbles inside it and you really want to avoid that because

the air will keep traveling through the sidewalls continuously and it will keep the tire making weaker and weaker on the side walls that’s where the sealants come in they take care of that problem and also the occasional flats that you usually have.

I did a separate in-depth article on Bubble In Tubeless Bike Tires-Why they can be dangerous if you had like to read more about this phenomenon.

and unlike non-UST TBR or conventional tires, any sealant would go for the tubeless tires but some are just better than others, and here’s why.

Best Sealants for tubeless (UST tires) :

Tubeless tires are pretty durable on their own and as I explained above they would work with or without a sealant and why you should put sealants in them as well.

The best sealants for tubeless tires would be latex-based sealants there are fiber-based sealants that don’t necessarily use the latex solution and use a fiber system which is good for sealing bigger holes but it doesn’t coat the inner side of the tire, that would actually prevent the bubbling in the tire and seal the holes from the inside.

you can use or buy whatever you like for me I usually use stans and orange seal sealants they are really good and reliable one thing to keep in mind is to cover the rim with rim tape whether or not the spokes are exposed on the rims or not because these sealants do contain some amounts of ammonia and that can accelerate rusting.

Tubeless-ready or conventional tires need sealants here’s why :

These tires do lose air and they necessarily need a sealant to prevent air leakage from the side walls of the tires and from the bead as well.

The reason for this is that these are porous and if you have never experienced it, they do it and when you seat a new tire on a conventional rim the bead will not hold the air or leak sealant for a while usually it gets better in 2 to 3 days and sealant leakage stops from the side walls as well as the bead.

So you can’t necessarily use these tires without a sealant if you do you will find them losing air overnight.

and in this case, they need rim tape as well in the rim bed and also on the sidewalls as well it basically prevents air leakage from the spoke holes and protects the rim from sealant as well.

If you encounter sealant dripping through the side walls or through spokes for a longer period of time the problem is usually with the rip tape and not necessarily with the sealant.

I did a separate article on Can you go tubeless with any tire | Here’s what you would need to do if you had like to read more about this topic.

Best tubeless Sealants for tubeless or conventional tires if you use them as tubeless tires :

Again for the tubeless-ready and conventional tires, I would recommend using latex sealants rather than using the new fiber-based sealants.

I have nothing against fiber-based sealants they are really great for tubes and big punctures that latex-based sealants may take time to seal but these are best as far as an inner coating on the tires goes.

and as for the TBR and conventional tires, the inner layers in the tires are not that great and the casing is porous as well and they usually leak through them as I explained above.

and one other thing that I should mention is that don’t use homebrew sealants or at least make sure that they don’t have propylene glycol in them in large amounts because that would internally eat the tire out so always make sure that you check the ammonia levels and propylene glycol or glycols in general in sealants and make sure that they are not in high concentration because they can damage the tires or the rim.

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